A secondary battery generally includes an electrode assembly, a case, and a cap assembly. The electrode assembly is formed by a positive electrode sheet, a negative electrode sheet, and a separating membrane disposed between the positive electrode sheet and the negative electrode sheet that are wound around a winding axis. The electrode assembly is received in the case, and the cap assembly is assembled with the case and disposed in correspondence to an end portion of the electrode assembly along the winding axis. The cap assembly includes a cap plate and an electrode terminal disposed on the cap sheet, wherein an electrode tab of the electrode assembly is electrically connected with the electrode terminal of the cap assembly. The cap plate is provided with a liquid injection hole communicating with a sealed space.
However, since the liquid injection hole on the cap plate and the end portion of the electrode assembly along the winding axis are opposite to each other in position, when an electrolyte is injected into the case through the liquid injection hole (in order to increase an efficiency of the electrolyte injection, it is generally necessary to increase a pressure of the electrolyte injection), the electrolyte will impact the end portion of the electrode assembly along the winding axis. In this case, as the impact force from the electrolyte is too large, deformation and shift of the separating membrane between the positive electrode sheet and negative electrode sheet at the end position may occur, causing the positive and negative electrode sheets to contact with each other and thus causing a short circuit.